Defined in header <stddef.h> Defined in header <stdio.h> Defined in header <string.h> Defined in header <time.h> typedef /*implementation-defined*/ size_t; size_t is the unsigned integer type of the result of sizeof , alignof (since C11) and offsetof. Notes size_t can store the maximum size of a theoretically possible object of any type (including array). size_t is commonly used for array indexing and loop counting. Programs that us

Defined in header <string.h> int strcmp( const char *lhs, const char *rhs ); Compares two null-terminated byte strings lexicographically. The sign of the result is the sign of the difference between the values of the first pair of characters (both interpreted as unsigned char) that differ in the strings being compared. The behavior is undefined if lhs or rhs are not pointers to null-terminated byte strings. Parameters lhs, rhs - pointers to the null-terminated byte

Defined in header <stdatomic.h> void atomic_flag_clear( volatile atomic_flag* obj ); (1) (since C11) void atomic_flag_clear_explicit( volatile atomic_flag* obj, memory_order order ); (2) (since C11) Atomically changes the state of a atomic_flag pointed to by obj to clear (false). The first version orders memory accesses according to memory_order_seq_cst, the second version orders memory accesses according to order. The argument is pointer to a volatile atomic flag to

Defined in header <complex.h> #define _Imaginary_I /* unspecified */ (since C99) The _Imaginary_I macro expands to a value of type const float _Imaginary with the value of the imaginary unit. As with any pure imaginary number support in C, this macro is only defined if the imaginary numbers are supported. A compiler that defines __STDC_IEC_559_COMPLEX__ is not required to support imaginary numbers. POSIX recommends checking if the macro _Imaginary_I is defined to identify

Defined in header <complex.h> float complex ctanf( float complex z ); (1) (since C99) double complex ctan( double complex z ); (2) (since C99) long double complex ctanl( long double complex z ); (3) (since C99) Defined in header <tgmath.h> #define tan( z ) (4) (since C99) 1-3) Computes the complex tangent of z. 4) Type-generic macro: If z has type long double complex, ctanl is called. if z has type double complex, ctan is called,

Defined in header <wctype.h> wctype_t wctype( const char* str ); (since C95) Constructs a value of type wctype_t that describes a LC_CTYPE category of wide character classification. It may be one of the standard classification categories, or a locale-specific category, such as "jkanji". Parameters str - C string holding the name of the desired category The following values of str are supported in all C locales: value of str effect "alnum" identifies the ca

Defined in header <wchar.h> wchar_t *wmemset( wchar_t *dest, wchar_t ch, size_t count ); (since C95) Copies the wide character ch into each of the first count wide characters of the wide character array (or integer array of compatible type) pointed to by dest. If overflow occurs, the behavior is undefined. If count is zero, the function does nothing. Parameters dest - pointer to the wide character array to fill ch - fill wide character count - number of

Defined in header <complex.h> #define complex _Complex (since C99) This macro expands to a type specifier used to identify complex types. A program may undefine and perhaps then redefine the complex macro. References C11 standard (ISO/IEC 9899:2011): 7.3.1/4 complex (p: 188) C99 standard (ISO/IEC 9899:1999): 7.3.1/2 complex (p: 170) See also imaginary (C99) imaginary type macro (macro constant)

An object whose identifier is declared without the storage-class specifier _Thread_local, and either with external or internal linkage or with the storage-class specifier static, has static storage duration. Its lifetime is the entire execution of the program and its stored value is initialized only once, prior to program startup. Notes Since its stored value is initialized only once, an object with static storage duration can profile the invocations of a function. The other use of the keywo

Defined in header <math.h> #define signbit(arg) /* implementation defined */ (since C99) Determines if the given floating point number arg is negative. The macro returns an integral value. Parameters arg - floating point value Return value Nonzero integral value if arg is negative, ​0​ otherwise. Notes This macro detects the sign bit of zeroes, infinities, and NaNs. Along with copysign, this macro is one of the only two portable ways to examine the sign of